The present invention relates generally to a valving mechanism for an internal combustion engine and, more specifically, to a gap self-compensating hydraulic rocker arm.
In an internal combustion engine, the motion of a valve generally exerts a great influence upon the volumetric efficiency, the noise of the engine, and the durability of the valve; and whether or not a valving mechanism is designed in a proper manner influences the performance, the economy, and the durability of the engine.
As the number of revolutions of an engine increases, the inertia force of a valving mechanism increases, until the whirling motion of a valve rises, the regulating time of the valve is rendered irregular, and the suctioning efficiency of the valve deteriorates, which results in deterioration in the performance of the engine and an increase in the seating sound of the valve, to thus increase not only the noise of but also stress on the valve, until the valve breaks as a result of fatigue.
Furthermore, at least one part of the valving mechanism, is subjected to thermal deformation at the time of the operation of the engine in correspondence to the state thereof. For preventing the valve from being kept open by thermal expansion of the valving mechanism, the linkage mechanism of the valving mechanism is provided with appropriate clearances. Excessive clearance of the valve causes the air-tightness of the valve to be rendered defective in the course of the operation thereof. An oil lifter is what is specifically employed for assuring automatic control of this clearance.
In the conventional valving mechanism provided with a rocker shaft and a rocker arm, an automatic control mechanism having a large quantity of oil contained therein, hence being large in mass, is arranged at the top of the rocker arm at a position that is spaced far apart from the center of the rocker shaft. Therefore, the inertia mass of the moving part thereof becomes extremely large, which constitutes a problem in terms of reducing the maximum number of revolutions and decreasing the durability of an internal combustion engine.